1. Field of the Invention
This invention relates to a sign plate for an illuminated sign. The sign plate includes a base plate made of light transmitting material with an opaque reflective layer or coating on at least one side of the light transmitting base plate. The integrity of the opaque reflective layer is broken by zones that form a configuration defining a message, art display, or other matter or intelligence communicated when the sign plate is illuminated. A corresponding configuration, but of light reflective material, is provided on the opposite side of the base plate. The sign plate also includes a light diffusion layer that receives and disperses light from the light source. By a particular arrangement of opaque surfaces and reflective surfaces relative to the light diffusion layer and an adjacent light source, electromagnetic radiation in the form of visible light from the light source is controlled to provide an aura that enhances formed outlines or contours of light around the communicated matter of the sign plate.
2. Description of the Related Art
An illuminated sign of this nature is disclosed in U.S. Pat. No. 5,009,019. In that invention an aura is created around an outline of the configuration being communicated by the sign. This aura is achieved by fluorescent material totally covering broken zones in an opaque layer on the sign plate. The fluorescent material is cut in the form of the configuration from a sheet of fluorescent plastic and is applied on the surface of the light transmitting base plate opposite the surface having the opaque layer or coating that is broken into the zones, and these zones correspond to the desired configuration to be communicated. The configuration made from the fluorescent plastic may be cut from a sheet by, for example, a router. This configuration when applied to the face of the base projects away from the base surface. The projection is on the front of the sign plate in that invention, i.e., the face of the sign plate that faces the viewer when the sign plate is in use.
The light source is directed toward the rear of the sign plate, i.e., the face of the sign plate opposite the viewer. In that invention, the most effective results are achieved when the light source is ultraviolet light, and the light rays pass forward through the openings of the broken zones of the opaque layer through the base plate and then into the fluorescent material, activating the fluorescent material.
A layer of opaque reflective material is placed on the front surface of the projecting fluorescent material that faces the viewer. This opaque reflective material is preferably of a smaller dimension than the broken zones, and so light emits around the edges only of the light reflective material, producing an outline or contour of the configuration being communicated. Accordingly, part of the light rays from the activated fluorescent material pass through the exposed side edges of the fluorescent material, while other rays are reflected off the light reflective layer back through the fluorescent material thence through the light transmitting base plate to its rear face to strike the front of the opaque reflective layer on the rear of the base plate. From there, the rays are reflected forwardly toward the viewer. These reflected rays create the aura around the outline.
For a viewer facing the sign plate, the effect achieved in that construction is that of glowing outlines and aura around the configuration of the matter being communicated, such as text or figures or art work.
The invention of the '019 patent is a vast improvement over the prior art known when its application was filed. For example, Danish Patent Application No. 4729/87, published under the Patent Cooperation Treaty in Publication WO-A-89,02637 on Mar. 23, 1989, discloses a transparent or ultraviolet translucent plate or sheet, the front side of which is covered with an ultraviolet, opaque layer or coating broken into zones corresponding to a text or a figure. Grooves are cut into the transparent sign plate around these zones, and strings of fluorescent plastic material are set into these grooves, both steps being somewhat difficult to accomplish and time consuming.
The invention of the '019 patent is also an improvement over U.S. Pat. No. 3,978,599 to Berger, wherein the text material projects rearwardly away from the viewer and toward the light source to gather light and enhance the amount of light seen directly by the viewer to reveal the whole of the configuration of broken zones in the opaque layer. No light reflective surface covers the openings of these broken zones, and so the viewer sees the whole text lighted rather than an outline and aura around the text.
The invention of the '019 patent is also an improvement over the sign plate disclosed in U.S. Pat. No. 2,071,239 to Spencer et al., wherein an excavating operation (preferably performed by sand blast) is utilized to form a design, letter or legend in solid bodies of glass which then protrude in bold relief from a roughened temporary surface left by the sand blasting operation to form protruding lens-like bodies of translucent or transparent material standing out in strong relief with respect to a background of contrasting character. It appears that the ambient light reflects variously from the resulting differing surfaces to create certain effects.
The invention of the '019 patent is also an improvement over U.S. Pat. No. 1,887,523 to Schenkel. The Schenkel reference utilizes opaque (black) layers. Black blocks light but does not reflect light. The Schenkel reference shows ways of blocking light to achieve the illusion of depth and shaded effect to simulate blocked letters or gas filled tubes (Column 1, lines 32-34), but the reference does not show or suggest reflecting surfaces to guide light rays for enhancing effects, such as creating an aura around an outline or contour of the matter to be communicated.
In contrast to the devices of these references, the structure disclosed in the '019 patent is easier and less expensive to produce and, in addition, provides effects not achieved in those devices. The structure of the '019 patent creates a particularly strong outline with aura around the matter to be communicated, especially if the side edges of the projecting fluorescent material are in general register on the front side of the base plate with the configuration of the broken zones on the rear side of the plate and if the side edges are inclined in relation to the sign plate's front face. In this connection, the inclined edges preferably form an angle of about 120 degrees to about 150 degrees with respect to the front face of the sign plate.
In accordance with the '019 patent, the text or figures or art work will be exceptionally clear if a layer of color is additionally placed on the front light reflective layer, especially if that color is different from the color of the remaining part of the sign plate. Thus, in a preferred structure of that invention, the opaque layer is provided on the rear of the foundational or light transmitting plate, but with a layer of color first applied intermediate the rear face of the light transmitting plate and the front face of the opaque layer. This structure allows the color to be seen through the light transmitting plate from the front, giving the sign its base color. The opaque layer in that invention may also be of a light reflective material or at least include a light reflective layer on its rear face to reflect light from the light source and increase the overall light emission from the sign plate in its operational condition.
Nonetheless, experience with the device of the '019 patent has revealed elements that desirably should be improved. For example, the light source preferably is ultraviolet (black) light. A sign built in accordance with that invention is most effective, therefore, in only low light or dark ambient conditions. It exhibits low illumination output and the aura is less pronounced in indoor lighting and daylight conditions. Furthermore, the forming of the fluorescent plastic into the desired configuration by the process of routing, including the preparation phases both before and after the routing, is labor intensive and a relatively slow process, affecting the costs of production and the ability to provide sample forms quickly at less costs. Even though mill-cutting in an automatic process, or molding or casting might reduce some of the labor costs per unit, the placing of the fluorescent materials on the sign plate is done by hand and requires accurate and skilled handwork.
Accordingly, it is desired to provide a sign plate producible by methods resulting in still higher productivity, more flexibility, and less costs and having a structure providing a brighter light output. Such a sign plate then could be released from its dim operating surroundings and be useful in daylight surroundings, thereby becoming a more acceptable product in the market. Space taken by the complete sign box is another consideration. The light source, to be most effective in the '019 patent, is preferably spaced a distance from the rear of the sign plate and away from the opaque layer to allow more of the rays to pass through the openings of the zones broken in the opaque layer for transmission through the thickness of the base plate to reach and activate the fluorescent plastic on the front side of the base plate. The space between the light source and the base plate, of course, restricts the minimum thickness or depth of the physical construction of the sign box that contains the sign plate and the light source.